The present invention relates generally to steerable catheters and catheter procedures involving functional devices, such as laser delivery devices and drug delivery devices. More particularly, the invention relates to a steerable catheter and method of use, particularly adapted for laser-assisted Percutaneous Transmyocardial Revascularization (PTMR). The distal tip of the catheter for guiding a laser delivery device, drug delivery device or other functional device extendable there through, is deflectable in at least one given plane. The invention includes an automatic catheter tip alignment system for maintaining constant relative positioning between the distal tip of the functional device and the distal tip of the steerable catheter. The invention also includes a surface contact detection system to detect contact with an interior body surface, such as the heart wall.
In the treatment of heart disease, one method of improving myocardial blood supply is called transmyocardial revascularization (TMR), the creation of channels in the myocardium of the heart. The procedure using needles in a form of surgical xe2x80x9cmyocardial acupuncturexe2x80x9d has been used clinically since the 1960s. Deckelbaum. L. I., Cardiovascular Applications of Laser Technology, Lasers in Surgery and Medicine 15:315-341 (1994). The technique relieves ischemia by allowing blood to pass from the ventricle through the channels either directly into other vessels communicating with the channels or into myocardial sinusoids which connect to the myocardial microcirculation.
In the reptilian heart, perfusion occurs via communicating channels between the left ventricle and the coronary arteries. Frazier, O. H., Myocardial Revascularization with Laser-Preliminary Findings, Circulation, 1995; 92 [suppl II]:II-58-II-65. There is evidence of these communicating channels in the developing human embryo. In the human heart, myocardial microanatomy involves the presence of myocardial sinusoids. These sinusoidal communications vary in size and structure, but represent a network of direct arterial-luminal, arterial-arterial, arterial-venous, and venous-luminal connections. This vascular mesh forms an important source of myocardial blood supply in reptiles but its role in humans is poorly understood.
Numerous surgical TMR studies have been performed, including early studies using needles to perform myocardial acupuncture, or boring, to mechanically displace and/or remove tissue. Such studies have involved surgically exposing the heart and sequentially inserting needles to form a number of channels through the epicardium, myocardium, and endocardium to allow blood from the ventricle to perfuse the channels. The early studies using needles showed that the newly created channels were subject to acute thrombosis followed by organization and fibrosis of clots resulting in channel closure. Interest in TMR using needles waned with the knowledge that such channels did not remain open. However, interest in TMR procedures has recurred with the advent of medical lasers used to create TMR channels. Histological evidence of patent, endothelium-lined tracts within laser-created channels shows that the lumen of laser channels can become hemocompatible and resists occlusion. A thin zone of charring occurs on the periphery of the laser-created channels through the well-known thermal effects of optical radiation on cardiovascular tissue. Additionally, recent histological evidence shows probable new vessel formation adjacent collagen occluded transmyocardial channels, thereby suggesting benefits from TMR with or without the formation of channels which remain patent.
Surgical TMR procedures using laser energy have been described. U.S. Pat. No. 4,658,817 issued Apr. 21, 1987 to Hardy teaches a method and apparatus for surgical TMR using a CO2 laser connected to an articulated arm having a handpiece attached thereto. The handpiece emits laser energy from a single aperture and is moved around the surface of the heart to create the desired number of channels. U.S. Pat. No. 5,380,316 issued Jan. 10, 1995 to Aita et al. purports to teach the use of a flexible lasing apparatus which is inserted into the open chest cavity in a surgical procedure. A lens at the distal end of the flexible apparatus is used to focus laser energy, and the apparatus is moved about the surface of the heart to create the desired number of channels.
The foregoing discussion relates to surgical procedures, i.e. procedures which access the heart surgically, either via open heart surgery, or perhaps by minimally invasive surgical (MIS) methods if the design and size of the distal ends of the hand pieces are suitable for use in an MIS site. However, since TMR most often involves creating channels through the epicardium into the lower left chamber of the heart, it is desirable to create TMR channels in a percutaneous procedure, i.e. by extending a catheter apparatus through the vasculature into the ventricle and creating the channels through endocardial surfaces and into myocardium. Performing percutaneous TMR (PTMR) is desirable for a number of reasons. Percutaneous catheter procedures are typically less traumatic to the patient compared to surgical procedures. Adhesions between the pericardial sac and epicardium are eliminated. Percutaneous TMR with a catheter apparatus also offers an alternative solution to persons who are not candidates for surgical procedures.
Because TMR procedures generally involve creating a plurality of channels within the myocardium, performing the procedure percutaneously requires the ability to steer a catheter apparatus through the vasculature and maneuver the apparatus within the ventricle of the beating heart as rapidly as possible to create the channels without subjecting the heart to the undue stress of a lengthy procedure. Additionally, the ability to control and stabilize the catheter apparatus against the beating heart wall while creating channels with a laser is desirable for percutaneous procedures to ensure creation of channels as desired and to ensure that the laser, or other energy source, is fired only within the myocardial tissue. For example, if the energy source is activated prior to wall contact, such activation may lead to the coagulation of blood and result in emboli. TMR channels should be spaced and grouped appropriately to achieve the desired result without weakening or rupturing the heart muscle.
The early myocardial acupuncture procedures were not performed percutaneously. The Hardy CO2 laser delivery system described above is rigid, relatively large, and not adaptable for percutaneous use. The Aita ""316 patent does not suggest a method for percutaneous use of the laser delivery device described therein for surgical use.
U.S. Pat. No. 5, 389,096 issued Feb. 14, 1995 to Aita et al. purports to teach one method of percutaneous TMR using an elongated flexible lasing apparatus with control lines and a focusing lens structure at the distal tip. The method uses pressure applied manually to attempt to stabilize the apparatus against the wall of the heart.
Several patents describe the use of catheters within the ventricle for percutaneous treatment of ventricular tachycardia. Such devices have a means to locate an arrhythmia site and ablate the site, at or just below the ventricle surface, using an electrode device or laser energy. U.S. Pat. No. 5,104,393 issued Apr. 14, 1992 to Isner teaches a catheter apparatus having a guiding Y-shaped sheath and guide catheter assembly for introducing an optical fiber into the ventricle. Positioning is described to enable a single burst of laser energy from a single aperture to ablate the site.
U.S. Pat. No. 5,255,679 issued Oct. 26, 1993 and U.S. Pat. No. 5,465,717 issued Nov. 14, 1995 respectively to Imran and Imran et al., disclose non-laser, basket-shaped catheter apparatus for mapping and/or ablation of arrhythmia sites within the ventricle. A pull cable is used to expand the basket portion within the ventricle, and a plurality of electrodes on the arms of the basket are used for ablation. The basket device is designed to place the electrodes on the ventricle wall.
U.S. Pat. No. 5,190,050 issued Mar. 2, 1993 to Nitzsche teaches a steerable catheter with a handle and a tube, the distal tip of which may be selectively curved by controllably moving one of three flat, sandwiched shims relative to the others by manipulation of a handle portion.
U.S. Pat. No. 5,358,479 issued Oct. 25, 1994 to Wilson, incorporated herein in its entirety by reference, teaches another steerable catheter with a handle and an inner tube, the apparatus having a single elongated, substantially flat shim spring mounted within the tip of the catheter tube, the shim having at least one transverse or lateral twist which causes the tip of the catheter tube to assume a desired curvature.
Drug therapies with angiogenic growth factors may expedite and/or augment collateral artery development. U.S. Pat. No. 5,498,238 issued Mar. 12, 1996 to Shapland et al., discloses a method simultaneous angioplasty and drug delivery to localized portions of arteries. The patent teaches the use of an expandable balloon end type catheter which can be filled with a drug-containing fluid and which is allowed to permeate through a semi-permeable membrane of the balloon-tip end and thereby be delivered directly to the surface of arteriosclerotic lesions on stenosed arteries.
A great deal of published scientific information concerning therapeutic agents is currently available on the internet. One company, Annual Reviews is located at http://www.annurev.org. A list of genetically engineered and/or naturally occurring drugs or other agents having pharmacological, therapeutic, diagnostic or other utility is located at http://www.annurev.org/sup/in/im15/im15b.htm. Additional scientific information is available at http://darwin.bio.uci.edu/cchughes/index.html.
Devices for effectuating drug injection have included non-articulating, viewing devices. U.S. Pat. No. 5,685,853 issued Nov. 11, 1997 to Bonnet teaches of a partially rigid endoscope to which is attached an injection or aspiration cannula that is axially adjustable along the shaft of the endoscope.
U.S. Pat. No. 5,261,889 issued Nov. 16, 1993 to Laine et al. teaches of an injection therapy catheter that is insertable through a working channel in an endoscope for delivering fluid agents through a hollow needle at the distal end of the catheter.
U.S. Pat. No. 5,685,853 issued Nov. 11, 1997 to Bonnet teaches an injection device by means of an injection cannula axially adjustable along an endoscope shaft. The injection cannula and guide tube are axially adjustable relative to the endoscope shaft by means of a handle which can be operated with one hand.
U.S. Pat. No. 4,350,148 issued Sep. 21, 1982 to Sivak, Jr. et al. also teaches of a drug injector device, in this case for treating esophageal varices. A flexible shafted endoscope has a conduit with distal ended needle is inserted in the endoscope""s biopsy channel for effectuating the treatment.
Prior devices also include viewing devices for cardiac interventional procedures. U.S. Pat. No. 4,784,133 issued Nov. 15, 1988 and U.S. Pat. No. 4,976,710 issued Dec. 11, 1990, both to Mackin, both teach of a flexible angioscope/bronchoscope device with an inflatable balloon structure for viewing intravasculature structures. These flexible catheter devices include a ported working channel for introduction of a working device and positioning of the working device at the viewing/treatment distal end.
U.S. Pat. No. 5,554,114 issued Sep. 10, 1996 to Wallace et al. teaches an infusion device with preformed shape. An infusion guidewire or catheter is used for introduction of the device through a selected path in a patient""s vascular system. An elongated tubular diffusion body lies at the distal end of an elongated tube, the diffusion portion having a plurality of infusion ports through which blood, drug, diagnostic agent or other material can be delivered to the particular site in the vascular system.
U.S. Pat. No. 5,464,394 issued Nov. 7, 1995 to Miller et al. teaches a multilumen percutaneous angioscopy catheter which allows simultaneous irrigation and passage of an angioscope there through.
U.S. Pat. No. 4,702,260 issued Oct. 27, 1987 and U.S. Pat. No. 4,766,906 issued Aug. 30, 1988, both to Wang, teach bronchoscopic needle assemblies. The needle assemblies are especially adapted for safe and efficacious collection of biopsy samples.
U.S. Pat. No. 5,409,453 issued Apr. 25, 1995 to Lundquist et al. teaches a steerable medical probe with stylets. The device is designed for reducing the mass of a body part, such as for biopsy sampling or for removing prostatic tissue in the case of BPH. The torquable catheter has a control end and a probe end, the probe end having a stylet guide means with a flexible tip and a tip directing means extending from the control end to the flexible tip for changing the orientation of the central axis of the stylet guide means for directing a flexible stylet outward through the stylet port and through intervening tissue to targeted tissues.
U.S. Pat. No. 5,571,151 issued Nov. 5, 1996 to Gregory teaches a method for contemporaneous application of laser energy and localized pharmacologic therapy. The method comprises preparing a solution of a pharmacologic agent, inserting the catheter into the lumen, directing the catheter to the site, transmitting visible light to the site, flowing the light transmissive liquid through the catheter, viewing the site, transmitting laser energy through the liquid filled catheter to treat the site, and introducing a flow of the pharmacologic agent in solution into the catheter for contemporaneous discharge at the distal end into the lumen adjacent the site.
International Publication No. WO 92/10142 published Jun. 25, 1992 by Pfizer Hospital Products Group and Makower teaches a device and method for interstitial laser energy delivery. A catheter with moveable needle system places one or more fiber optic elements and thermo-measuring devices through a body passageway wall and into the bulk of an adjacent organ. The catheter is positioned adjacent to the organ and the needles are extended to mechanically puncture the wall and move into the organ with the fiber optic elements. The needle may be withdrawn into the catheter before delivery of laser energy or remain in the organ to serve as an aspiration-irrigation vehicle. Lumens provided within the catheter for carrying the hollow needles may likewise be used for respiration or irrigation of the passageway. The devices may also be used with a dilatation balloon, etc.
U.S. Pat. No. 5,386,837 to Sterzer discloses an xe2x80x9celectrochemotherapeuticxe2x80x9d technique for treating tumors in which high intensity electromagnetic force fields (including a laser) are applied to the body after chemotherapy has been applied. This is intended to create large, transient pores in individual cells of a superficially-seated tumor lesion located between individually mounted ceramic horn antennae by non-invasively applying a highly directional beam of force-field shock of HF pulsed wave energy into the cells, thus inducing the drug to enter the cells.
The use of superelastic and/or shape memory materials is widely known. Structure and Properties of Tixe2x80x94NI Alloys: Nitinol Devices and Components, Duerig et al., In Press, Titanium Handbook, ASM (1994) In general, binary compositions of Nickel (Ni) and Titanium (Ti), yield alloys with shape memory and superelastic properties. These alloys are commonly referred to as Nixe2x80x94Ti, nitinol, and other industry names. Their precise physical and other properties of interest are extremely sensitive to the precise Ni/Ti ratio used. Generally, alloys with 49.0 to 50.7 atomic % of Ti are commercially available, with superelastic alloys in the range of 49.0 to 49.4%, and shape memory alloys in the range of 49.7 to 50.7%. Due to a rapid decrease in the ductility of the material, binary alloys with less than 49.4 at. % Ti are generally unstable. In general, these types of materials exhibit hysteresis, defined as a phenomenon exhibited by a system whose state depends on its previous history, and illustrated diagrammatically by the familiar upper and lower curves which meet at the ends and define an area under the curves. In the case of solid materials undergoing elastic hysteresis (as opposed to magnetic or electrical hysteresis), the curves are related to stress necessary to cause deformation or otherwise overcome existing stress in pre-stressed materials.
For the purposes of this disclosure, a distinction between superelastic materials and shape memory materials is made. Superelasticity refers to the highly exaggerated elasticity, or springback, observed in many Nixe2x80x94Ti alloys deformed at a specific temperature. The function of the material in many of such cases is to store mechanical energy. Though limited to a rather small temperature range, these alloys can deliver over 15 times the elastic motion of a spring steel, i.e., withstand a force up to 15 times greater without permanent deformation. Shape memory materials will refer to those materials which can be deformed, but which will freely recover their original shapes during heating, often utilizing electrical resistivity, or which will develop a large recovery stress when recovery is prevented. With regard to the present invention, it will be understood that the transition temperature of materials must, in general, be somewhat above body temperature.
U.S. Pat. No. 3,890,977 issued Jun. 24, 1975 to Wilson teaches kinetic memory electrodes, catheters and cannulae. These devices incorporate a material, such as a Nixe2x80x94Ti alloy, having heat-activated mechanical memory properties. The device is formed into an operative shape at a high temperature. Then, at a low temperature below its transitional temperature, it is reformed into a shape for ease of insertion into a guide catheter or the like or otherwise through a portion of a patient""s vasculature or other body lumen. When located in the organ or other desired region, those portions of the device constructed using such shape memory materials are heated to above their transitional temperatures, using electrically resistive elements, thereby returning the catheter to its original annealed anchoring or proper locating shape. An important drawback of the Wilson apparatus is that heat must be applied to the catheter tip. Complicated construction and electrical power distribution must be considered.
U.S. Pat. No. 5,114,402 issued May 19, 1992 to McCoy teaches a maneuverable distal apparatus with a temperature activated material of construction which, upon heating to a predetermined position, will assume a predetermined, memorized shape, and which upon cooling, will assume a different shape by action of a spring element urging the apparatus into the different shape.
U.S. Pat. 4,846,171 issued Jul. 11, 1989 to Kauphusman et al. teaches a transluminal angioplasty catheter with a fiber advancing housing with a Hall effect sensor for control of a laser irradiation source that cooperates with the fiber advance mechanism.
There is a need for steerable percutaneous catheters, especially PTMR steerable catheters which automatically maintain alignment of the distal end of the catheter with the distal end of a functional device therein during catheter deflection movement relative to an interior body surface, particularly a ventricular wall. Moreover, there is a need for a mechanism to detect interior body surface contact with the distal tip of the catheter.
Thus, it is an advantage of the present invention to provide a steerable catheter and method of use for percutaneous and other intra-vascular procedures, including but not limited to PTMR, or any stimulation procedure.
The steerable percutaneous catheter of the present invention comprises a catheter jacket having proximal and distal ends, and at least a first lumen, at least a first one functional device within the lumen of the catheter jacket, the functional device having proximal and distal ends, a deflection mechanism at the proximal end of the catheter, the deflection mechanism operatively attached to a deflector device at the distal end of the catheter jacket, activation of the deflector device by movement of the deflection mechanism deflects the distal end of the catheter jacket and the functional device therein; and a relative movement compensation mechanism for maintaining. alignment between the catheter jacket and the functional device whereby movement of the deflecting mechanism causes simultaneous movement of the relative compensation movement mechanism.
It is a further advantage of the present invention to provide a steerable catheter capable of being guided into a heart chamber and used therein for creating a plurality of TMR channels controllably and efficiently that can maintain tip alignment during motions of the distal section of the catheter. It is a further advantage of the present invention to provide an elongated steerable catheter for placement within a heart chamber, organ aperture or other body opening, the steerable catheter having an inner tube extending there through, the inner tube for guiding a laser delivery device or other functional device to selected surfaces of the heart chamber, organ aperture or other body opening or body surface for laser or other treatment thereon, particularly adapted for laser-assisted transluminal revascularization (TMR) and further including a mechanism for maintaining a constant positional relationship between the translatable laser delivery device or other functional device and the distal tip of the catheter during catheter tip deflection.
It is yet a further advantage of the present invention to provide a percutaneous steerable catheter which can be positioned securely into a selected position within the left ventricle, or other body opening or cavity.
A further advantage of the present invention is to provide a steerable catheter with a tip alignment system which maintains precise alignment between the distal tip of the catheter and a laser delivery device such as fiber, bundle, other functional devices being inserted there through, etc., as the distal tip of the steerable catheter is deflected.
A further advantage of the present invention is to provide a steerable catheter which can be used for detection of contact and maintenance of contact between the distal tip of the catheter and the heart wall or other interior body structure or surface, such as during PTMR or stimulation.
A further advantage is to provide a steerable catheter with a handle portion at its proximal end and a controllably deflectable portion at its distal end.
The elongated corner or inner tube has a distal end, in the region where a curvature is to be formed, and an anchor sleeve is slidably disposed over the center or inner tube. The anchor sleeve is attached to the inside wall of the outer jacket and coupled to the distal end of the center or inner tube with a bendable member which extends between the distal tip of the steerable catheter and the anchor sleeve over the center or inner tube in a first embodiment. In a second embodiment of the center or inner tube, a shim is attached to the sleeve and a coil on the proximal end and is positioned in a key hole configuration. The distal section of the shim is attached to the distal tip of the catheter.
On the opposite the translation sleeve is a guide for a pull cable, the pull cable attached to the distal end of the steerable catheter and extending through the guide to the handle. Thus, the translation sleeve is maintained radially opposite the pull cable with the center or inner tube in between. An alternate design includes a spring in which a pull wire is attached to the distal end of the catheter without the shim.
An outer jacket has, in a preferred embodiment, distinct sections of different stiffness or durometer. One or more distinct sections of material of differing stiffness or durometer can be used. Junctions between the sections of different stiffness or durometer can be discrete and clearly defined, or they can blend smoothly or gradually. A distal, more flexible portion is coupled to a proximal, stiffer portion. The anchor sleeve is coupled to the outer jacket at or near the junction of two portions of the outer jacket in a first embodiment of the catheter body. A second embodiment has the shim coupled to the sleeve. Thus, the center tube moves freely through the anchor sleeve
Adjacent the handle, the proximal outer jacket portion terminates at the catheter base. The pull cable extends through the catheter base, through a deflection housing tube, and terminates in a cable stop. Rotation of a deflection knob threadably mounted onto the deflection housing tube will cause the pull cable to be pulled backward, or the outer jacket to be pushed forward, relative to each other, thereby inducing deflection of the distal end of the steerable catheter. Additionally, another degree of deflection can be implemented by use of an additional deflection wire at the distal catheter tip that is controlled by a knob or slide member on the catheter handle to achieve at least two degrees of deflection freedom at the catheter tip.
The elongated steerable catheter is designed to be placed into the vasculature of the patient and steered there-through until the distal tip is adjacent a selected portion of tissue, such as on an endocardial surface within the left ventricle. Thus, the distal tip of a laser delivery device, such as an optical fiber or fiber bundle or other functional energy delivery device such as radio frequency electrodes, microwave cutters, ultrasound transmitters, mechanical coring devices, fluids jets and the like, can be extended through the inner tube of the steerable catheter such that its distal tip comes into contact with the selected surface structure for treatment thereon. With regard to PTMR therefore, the energy delivery device can be controllably advanced through the steerable catheter for creating one or more PTMR channels. Furthermore, with regard to non-laser PTMR, a cannula or trocar assembly may be extended through the steerable catheter into the tissue of the ventricle, with or without use of a mechanical piercing tool.
In alternate embodiments, the steerable catheter of the present invention includes other functional devices including but not limited to, fiber advance depth control mechanism, visualization device, drug delivery apparatus, etc.
Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.